Rotary tube furnaces within direct heating are commonly used for physical and chemical conversions of both solids and powders. U.S. Pat. No. 6,042,370 discloses a furnace having a graphite tube inside an oxygen free chamber with graphite heating elements capable of heating to temperatures as high as 2800° C. It is known that graphite may be used as one of the construction materials in such furnaces. It is also known that furnaces operating at extreme temperatures frequently require that the treatment of the material being processed be carried out in an inert atmosphere, such as a non-oxidizing atmosphere, to avoid undesired reactions. In addition, when graphite is used as part of the furnace, it may also react with the oxygen and air at extremely high temperatures. Thus, it is known to provide an inert atmosphere enveloping the graphite furnace equipment as well as the material being processed.